Divide and conquer

Published 10:25 pm Thursday, August 12, 2010

Wondering why your daylilies or irises aren’t blooming like they have been the past few years?

It’s probably time to pull them up and divide them.

“You should divide them every few years,” said Linda Pinkham. “The reason being for daylilies, is that once get a certain amount of fans, they’re so crowded their performance declines. It’s the same with bearded irises, but it’s their rhizomes that will end up growing on top of each other.”

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Pinkham has more than 30 years of experience in horticulture. She graduated from Virginia Tech and worked for the Virginia Cooperative Extension Agency after college before joining her husband at Smithfield Gardens, which they founded. She now tends to their eight gardens, on their five-acre property, in which she has more than 700 daylilies and a variety of irises.

Around this time of year is when she begins the extensive task of dividing her daylilies and irises.

“Now that they’re done blooming, it is an ideal time to get them ready to go into the ground,” Pinkham said. “You don’t interrupt their blooming cycle, and they have time to root before the cold weather settles in.”

A daylily needs to be divided when it has more than 12 to 15 fans on it. An iris with rhizomes should be separated every 5 years if it blooms once a year or every three years if they bloom twice a year, Pinkham said.

It’s important to know what kind of iris you have, because not all have rhizomes that need to be separated.

To start separating, dig the plants up, one at a time. “Otherwise, you’ll mix up what kind you’re dividing,” Pinkham said. “They all look the same. If you don’t care, it’s not a big deal, but a name can be the difference between a $1 daylily and a $25 daylily.”

A trick Pinkham does to keep them in order is to write their names on the leaves with a magic marker.

After digging the plants up in a large clump, take off all the caps and stems, being careful not to mistake old for new growth.

Next, use a spade or clippers to trim the tender foliage off the top of the entire plant.

“It cuts down on the amount of moisture the roots need, which means it can put more energy toward sending those roots out,” Pinkham said.

Then, grab a root knife or a screwdriver, Pinkham’s tool of choice.

“A screwdriver doesn’t cut the roots,” Pinkham said. “You just need to make sure you have good leverage, so you don’t destroy the roots.”

Separate the fans of the daylilies into groups of two or three, and separate each iris plant from each other and dispose of the “mother bulb,” the original rhizome.

“Once a rhizome has bloomed, it won’t bloom again,” Pinkham said. “There’s no reason to keep it, and if it begins to rot it could spread to the other rhizomes.”

A rhizome that has already bloomed will either be shriveled or still have the round, thick stem attached. Rhizomes with leaves sprouting from them will still send out blooms.

When separating irises, it’s also a good idea to cut off any dark, mushy roots to keep rot away.

“They’re very susceptible to disease,” Pinkham said. “I always wash my rhizomes off with a solution of one cup of anti-bacterial hand soap to a gallon of water.”

After separating, you can wrap them in newspaper, put in an envelope and ship them to a friend or get them ready to plant.

If not going directly into the ground, both the iris and daylily should be put in pots about the same size as their root systems.

After putting in some root stimulator, cover the roots of the day lilies, but leave the tops of rhizomes exposed.

Then, whether they’re in the ground or in a pot, “give them a good water and don’t water them again until they take hold,” Pinkham said.

If all goes well, your flowers will be full bloomers next year.